Long-term changes in sewage sludge stored in a reed bed

The problem of the utilization and management of sewage sludge originating from small wastewater treatment plants is still unsolved. A common approach is to store the sludge in plots which in time turn into grassland. This investigation was aimed at evaluating the influence of the storage time in plots on the chemical properties of sewage sludge deposited there. Tests were carried out on samples obtained from discrete layers of stratified sludge that had lain in a hydrophyte facility disused for 7 years after 23 years of continuous sludge discharge. The age of the sludge was established by the lead-210 method. Moisture, organic matter, total nitrogen and total phosphorus contents were measured in samples of dated sewage sludge. The composition of the stored biosolids stabilized with respect to phosphorus, nitrogen and organic matter within 11, 15 and 17 years, respectively.